//               https://ac.nowcoder.com/acm/problem/50044





#include <iostream>
using namespace std;

int main()
{
	double ans = 1;
	int n, m, i;
	cin >> n >> m;
	for (i = 0; i < n - m; i++)
		ans *= 0.2;
	for (i = n; i >= n - m + 1; i--)
		ans *= i;
	for (i = m; i > 1; i--)
		ans /= i;
	for (i = 0; i < m; i++)
		ans *= 0.8;

	printf("%.4lf\n", ans);
	return 0;
}